Methylcobalamin is an active coenzyme form of vitamin B-12 that is more bioavailable that the common form, cyanocobalamin. B-12 is essential for healthy red blood cells, energy level, and DNA production, and plays an important role in maintaining normal nerve function. Older people tend to have less stomach acid, which may result in less absorption of B-12 from food. Supplementing with Source Naturals Methylcobalamin B-12 can help ensure adequate intake.